chore(default-flatpaks): Obtain flatpak list of apps without runtimes

[fiftydinar]

Since runtimes are not supported in our module, we don't need them in a flatpak list inside binaries.

[xynydev]

I still don't know why runtimes aren't supported...

[fiftydinar]

I still don't know why runtimes aren't supported...

1. I mentioned this once, but it's because Universal Blue images & ublue-update automatically remove unused flatpak dependencies, which can possibly remove runtime that user specified in the module recipe itself.

2. Another reason is that most flatpak runtimes have unstable branch versioning, which change over time.
   Users would need to change flatpak runtime versioning every time it updates, which is not very convenient at all.

3. Related to 2. reason, detection of same flatpak runtimes with different versions is tricky to do, which would be needed to detect which flatpak runtimes should remain as user specified runtime & which should not.
   However, even If I implemented this, it could still happen that runtime gets automatically removed by using flatpak uninstall --unused, which is outlined in 1. reason.